The roster was drawn up last February as part of a major reform of the Government’s relationship with marcoms agencies following the break-up of the COI. Unity was a new appointment, with the other five agencies being Engine Group, Munro & Forster, Consolidated, SKV Communications and Syndicate Communications.

Unity claimed it had been frustrated by what it called over-dependence on agencies' previous experience by the departments putting out work through the roster.

Unity co-founder Nik Done claimed that the agency had invested around £50,000 in staff time to get on to the roster and compete for briefs but, having failed to win work, had stopped pitching because of a scoring system "that encourages cronyism".

Emphasising that she understood experience was important, Done nonetheless claimed Whitehall figures were "covering their backs" in often opting for the safest, rather than best, work by giving direct previous experience too much importance when considering agency proposals.

Citing one tender in which previous experience made up 25 per cent of overall marks as an example, Done asserted that Unity’s record in behavioural change campaigns – including recent award-winning work for Cancer Research UK – had counted for little.

"I believed the new system would be based on the best responses to a brief," she said.

"If agencies have earned their place on the roster that should already show to some extent they are up to the job, and the decision should be based on how they have approached the problem in question.

"I have no problem with losing a pitch if an agency has had a stronger idea but just because someone has done the work before doesn’t mean they are the best placed to create great work."

"This isn’t about sour grapes," added Done. "We understand why agencies pair up and we understand that experience is important but we think the system is fundamentally flawed when it becomes a race to team up with the ‘right people’."

A government spokeswoman said the system, which is overseen by the Crown Commercial Service, was "a robust, transparent and fair tendering process that ensures we act as an intelligent customer for taxpayers".

Stating that it selected "those with the right skills and experience to deliver world-class communications", she added:

"This is working. Hundreds of thousands of people have become Dementia Friends, learning more about supporting people with the condition, and the GREAT campaign, which showcases the very best of what Britain has to offer, has so far won 17 awards and commendations.

"This is due in part to the great work of agencies on the frameworks. We are now building on this and are always seeking to improve the way we do business. As part of this, we will shortly be holding two events with our suppliers to gather their views."